AYUCR Electronics

Having wired the camera with external shutter leads I now
needed a way to trip them. They needed to be tripped (i.e.
connected together via a relay) at a regular interval, perhaps 2
seconds, starting at launch. I had read that a 555 timer chip
configured as a multivibrator can work. I purchased Engineer'sas
a timer. Mini-Notebook, 555 Timer Circuits (Radio Shack
Cat. No. 62-5010) and found the basis for the circuit I would
need.For launch detection I chose an acceleration switch from
Adept Rocketry. The acceleration switch and timer were both
powered by a single 9V battery.

Electronics Block Diagram

I built and tested the circuit using a breadboard and then
implemented it using a Radio Shack PC board kit (Cat. No. 276-1576).
This allowed me to etch my own PC board. If you decide the make
your own board for the circuit you will need a 3/64" drill
bit. These can be a little tough to find but larger drill bits
will make holes that are too large and make soldering very
difficult. I discovered this the hard way. I also recommed a
socket for the 555 IC as heat from soldering can damage ICs. The
ASA3T acceleration switch is smart enough to differentiate a bump
or jar from liftoff but I chose to add an arming plug (1/8"
Phono plug) just to be safe. Once prepped and loaded if the timer
starts accidentally there is no way to stop it before it wastes a
whole roll of film. While not strictly necessary it is recomended.

Part

Radio Shack Cat. No.

555 Timer IC

276-1723

8-Pin Low Profile Socket

276-1995

22 uF Capacitor

Various

47k Ohm Potentiometer (R1)

271-283

10K Ohm Resistor (R2)

271-1335

5VDC SPDT Relay

275-240

1N914 Switching Diode

276-1112

9V Battery Snap Connector

270-324

Optional

1/8" Phone Jack (closed circuit type)

274-248

1/8" Phone Plug (2 Conductor)

274-278

The IC pin numbers are listed on the 555 IC. Starting from the
top they are 8, 4, 3, 1, 2 and 6.

Timer Circuit Diagram

The finished board is shown below.

Timer Circuit Component Side

Timer Circuit Trace Side

The Yellow and Orange wires terminate in a Dean's connector
and connect to the Camera's shutter wires. The Red and Black pair
of wires connect to the output of an Adept ASA3T Acceleration
Switch. This device (shown below oriented horizontally) senses
liftoff and powers the timer circuit using via the same 9V
bettery powering the ASA3T. There is a POT on the ASA3T that
allows it to be configured to power up the timer anywhere from 1/2
to 15 seconds after liftoff. When used in AYUCR the time delay is
set to the minimum.